feat(provenance): post_id/artist_id gallery filters via EXISTS (mutually exclusive)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/app/services/gallery_service.py

@@ -10,10 +10,10 @@ import base64
 from dataclasses import dataclass
 from datetime import datetime
 
-from sqlalchemy import and_, func, or_, select
+from sqlalchemy import and_, exists, func, or_, select
 from sqlalchemy.ext.asyncio import AsyncSession
 
-from ..models import ImageRecord, Tag
+from ..models import ImageProvenance, ImageRecord, Source, Tag
 from ..models.tag import image_tag
 
 CURSOR_SEPARATOR = "|"
@@ -67,6 +67,31 @@ def thumbnail_url(sha256_hex: str, mime: str) -> str:
     return f"/images/thumbs/{bucket}/{sha256_hex}{ext}"
 
 
+def _require_single_filter(tag_id, post_id, artist_id) -> None:
+    if sum(x is not None for x in (tag_id, post_id, artist_id)) > 1:
+        raise ValueError(
+            "tag_id, post_id, artist_id are mutually exclusive"
+        )
+
+
+def _provenance_clause(post_id, artist_id):
+    """Correlated EXISTS clause (NOT a join) so an image with multiple
+    matching provenance rows is returned exactly once and the
+    (created_at DESC, id DESC) cursor ordering is unaffected."""
+    if post_id is not None:
+        return exists().where(
+            ImageProvenance.image_record_id == ImageRecord.id,
+            ImageProvenance.post_id == post_id,
+        )
+    if artist_id is not None:
+        return exists().where(
+            ImageProvenance.image_record_id == ImageRecord.id,
+            ImageProvenance.source_id == Source.id,
+            Source.artist_id == artist_id,
+        )
+    return None
+
+
 class GalleryService:
     def __init__(self, session: AsyncSession):
         self.session = session
@@ -76,15 +101,21 @@ class GalleryService:
         cursor: str | None,
         limit: int = 50,
         tag_id: int | None = None,
+        post_id: int | None = None,
+        artist_id: int | None = None,
     ) -> GalleryPage:
         if limit < 1 or limit > 200:
             raise ValueError("limit must be between 1 and 200")
+        _require_single_filter(tag_id, post_id, artist_id)
 
         stmt = select(ImageRecord)
         if tag_id is not None:
             stmt = stmt.join(image_tag, image_tag.c.image_record_id == ImageRecord.id).where(
                 image_tag.c.tag_id == tag_id
             )
+        prov = _provenance_clause(post_id, artist_id)
+        if prov is not None:
+            stmt = stmt.where(prov)
 
         if cursor:
             cur_ts, cur_id = decode_cursor(cursor)
@@ -123,22 +154,32 @@ class GalleryService:
             date_groups=_group_by_year_month(images),
         )
 
-    async def timeline(self, tag_id: int | None = None) -> list[TimelineBucket]:
+    async def timeline(
+        self,
+        tag_id: int | None = None,
+        post_id: int | None = None,
+        artist_id: int | None = None,
+    ) -> list[TimelineBucket]:
         year_col = func.date_part("year", ImageRecord.created_at).label("yr")
         month_col = func.date_part("month", ImageRecord.created_at).label("mo")
         stmt = select(
             year_col, month_col, func.count(ImageRecord.id).label("cnt")
         )
+        _require_single_filter(tag_id, post_id, artist_id)
         if tag_id is not None:
             stmt = stmt.join(image_tag, image_tag.c.image_record_id == ImageRecord.id).where(
                 image_tag.c.tag_id == tag_id
             )
+        prov = _provenance_clause(post_id, artist_id)
+        if prov is not None:
+            stmt = stmt.where(prov)
         stmt = stmt.group_by(year_col, month_col).order_by(year_col.desc(), month_col.desc())
         rows = (await self.session.execute(stmt)).all()
         return [TimelineBucket(year=int(r.yr), month=int(r.mo), count=int(r.cnt)) for r in rows]
 
     async def jump_cursor(
-        self, year: int, month: int, tag_id: int | None = None
+        self, year: int, month: int, tag_id: int | None = None,
+        post_id: int | None = None, artist_id: int | None = None,
     ) -> str | None:
         """Returns a cursor that, when passed to scroll(), positions at the
         first image of the given year-month. None if the bucket is empty.
@@ -149,10 +190,14 @@ class GalleryService:
             extract("year", ImageRecord.created_at) == year,
             extract("month", ImageRecord.created_at) == month,
         )
+        _require_single_filter(tag_id, post_id, artist_id)
         if tag_id is not None:
             stmt = stmt.join(image_tag, image_tag.c.image_record_id == ImageRecord.id).where(
                 image_tag.c.tag_id == tag_id
             )
+        prov = _provenance_clause(post_id, artist_id)
+        if prov is not None:
+            stmt = stmt.where(prov)
         stmt = stmt.order_by(ImageRecord.created_at.desc(), ImageRecord.id.desc()).limit(1)
         first = (await self.session.execute(stmt)).scalar_one_or_none()
         if first is None: